Splitting Tensile Properties of Hybrid Fiber Reinforced Ultra High Performance Concrete After Exposure to Elevated Temperatures

Ultra-high performance concrete (UHPC) is increasingly being used to reinforce and modify existing structures, but UHPC is prone to high temperature bursting under fire conditions, and how to improve the high temperature burst resistance of UHPC has become a hot topic in the current industry. In this paper, the effects of high temperature and secondary curing on the splitting tensile strength of UHPC compounded with steel and polypropylene fibers were investigated. The analyses were carried out that: 1) UHPC doped with 3% steel fiber and 0.4% PP fiber has good resistance to high temperature bursting, and even after the action of 900℃, the UHPC splitting and stretching specimen do not appear to burst and peel. 2) The tensile strength of UHPC splitting was improved by high temperature treatment at 300℃, which played a similar role to "steam curing", and the splitting tensile strength of UHPC after high temperature treatment at 600℃ and 900℃ decreased significantly, and the decline became more noticeable with higher temperatures. 3) The residual splitting tensile strength of UHPC after secondary curing is the same as that of UHPC without curing after high temperature. However, the difference is that as the temperature of the high temperature treatment increases, the effect of secondary curing on the residual strength of UHPC becomes more significant.